Apache newbie: map folder outside c:\apache2\htdocs to localhost

Thanks for spending some time to read a newbie question!

I have recently installed Apache2Triad to develop a web application
using PHP and mySQL. Before I had Apache2Triad installed, I uploaded
my php pages to my provider, and tested them online. I installed
Apache2Triad mainly to get rid of the uploading time delays (and to
have my own playground, of course).

From the documentation, I have understood that my pages should go
to the directory c:\apache2\htdocs. I created a subfolder MySite and
can now use http://localhost/mysite/index.php. Works fine.

However, the folder in which I originally developped the site has the
following structure (simplified):

c:\myproject
+--- supporting files
+--- templates
+--- libary
+--- mysite
+--- index.php
+--- my other php pages, images etc.

What I originally uploaded to my provider was only the contents of the
'mysite' subfolder.

With Apache, if I would move the entire folder "my project" under
"c:\apache2\htdocs", than I would create an additional level under
localhost, and I would have to use http://localhost/myproject/mysite
instead of just http://localhost/mysite.

My question: can I leave the files where they are (in c:\myproject)
and tell Apache that when I ask for http://localhost/mysite/index.php
it should get it from c:\myproject\mysite\index.php.

I am sure that this must be explained SOMEWHERE in the tons of
documentation, but I don't know what topic I should look for
(what feature should I search for).

I am just running Apache/php/mySQL/... to develop the site, I am not
using my PC to host it on the internet.
I use Windows XP Home Edition.

Any help or reference to the proper documentation files is welcome.
If I should have posted this question to another group instead, don't
hesiate to tell me.

Best regards,

Bert Geenen / Belgium